60 Penis in Palpatores and Laniatores 



in Phalangioidas it is only slightly curved upwards, in Ischyropsalis (PI. VI., fig. 18) its 

 distal portion is arched upwards rather strongly but gradually, in Nemastoma the species 

 differ in this respect. In N. argenteo-lunulatum it is arched rather strongly but evenly; 

 whilst in i\". lugnhre (PI. VI., fig. 20) it is curved strongly and abruptly, in front of its 

 expanded part, but the rest of its distal jjortion is almost straight. The most peculiar 

 feature of corpus penis in all Palpatoi'es is that it is thicker at its posterior extremity, 

 a shape due to the fact that the posterior portion, which varies as to its proportionate 

 length, contains a muscle, or — in Nemastomatoidae and Troguloidee — a pair of muscles, 

 with the respective tendon or tendons attached to the base of glans on the ventral side. 

 It is the shape of this muscular apparatus that determines the shape of corpus penis, 

 apart from its curvature, which is different in different species. The simplest form of corpus 

 penis is met with in Troguloidae (PI. VI., fig. 26) where it diminishes in thickness j^retty 

 evenly from the base to the end, as the pair of muscles {mc) almost reach to the apex of 

 corpus, and is furnished with a pair of short tendons (fig. 27, tnic). In this group corpus is 

 covered with thin skin, biit in its ventral side there is a long narrow strip, which is more 

 firmly chitinized, commencing near the anterior extremity of corpus and diminishing gradually 

 in width towards the posterior extremity ; the chitinized membrane of corpus shows a peculiar 

 marking, consisting of very fine transverse lines. Both these features are also found in 

 Nemastoma (PL VI., fig. 25) where corpus is firmly chitinized ; in N. lugubre the wall of corpus 

 must even be described as thick. In Phalangioidas the posterior, thicker portion of corpus 

 penis, which contains the muscle, is as a rule not sharply separated from the thinner and 

 more slender part. In Ischyropsalis (PI. VI., fig. 18) corpus is similar to the same organ in 

 Phalangioida;, but the anterior portion is much more slender, and its wall much more firmly 

 chitinized. Penis is of extraordinary length in Nemastoma ; in N. lugnhre, where it is longer 

 than in N. argenteo-lunulatum it is so long that, when quite drawn back it reaches past the 

 alimentary canal, on the right side of it, beyond anus towards the dorsal surface, in accordance 

 with its shai-p curvature, as far as the seventh tergite of abdomen, so that when penis is 

 entirely drawn back, m. retractores penis are directed forwards. A peculiarity in Nemastoma 

 is that the posterior portion, which here is much thicker, is somewhat flattened, remarkably 

 short and heavy, and thereby sharply separated from the very long and thin distal portion ; the 

 tendons of the pair of muscles contained in the thicker portion are accordingly of extreme 

 length. It is scarcely necessary to say that this apparatus serves to erect glans in Phalangioidas, 

 where it is bent backwards when at rest. In Sclerosomatini nobis, Ischyropsalidoidse, Nema- 

 stomatoidae and Troguloida?, where glans is directed forwards when at rest, of course no 

 erection can take place, and the muscular apparatus serves probably to stretch glans penis 

 down towards the ventral side as far as possible, acting in a way similar to that of the 

 muscle on the inside of the lower jaw between os articulare and os dentale, in many fishes, 

 for instance Coitus and Gadus. 



In the great majoritj- of Laniatores (PI. VI., figs. 29 and 32) penis differs not a little 

 in shape from that organ in Palpatores. Corpus penis is very slender through the whole 

 of its length, the posterior portion not being increased in bulk, as it does not contain 

 any muscles. The posterior extremity of corpus is expanded in the shape of a collar in 

 the place where it joins the .surrounding chitinized sheath ; it is a little thickened 

 anteriorly where it joins glans. This latter (c) is not by any means so abruptly separated 

 fronj corpus penis as is the case in the great majority of Palpatores, and it consists of 



